1. A device that has as its critical component a metal wire or strip that will melt when heated by a prescribed (design) amperage, creating an open in the circuit of which it is a part, thereby protecting the circuit from an overcurrent condition. Note: Fuses are often characterized as "fast-blow" or "slow-blow," according to the time required for them to respond to an overcurrent condition. Fast-blow fuses open nearly instantaneously when exposed to an overcurrent condition. Slow-blow fuses can tolerate a transient overcurrent condition, but will open if the overcurrent condition is sustained. 2. In optical fiber technology, to join the endfaces of a pair of optical fibers by melting, i.e., welding, the endfaces together.